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Soil Mechanics

NSSDCA ID: 1972-031C-09

Mission Name: Apollo 16 Lunar Module /ALSEP
Principal Investigator:Prof. James K. Mitchell

Description

The purpose of the soil mechanics experiment (S-200) was to obtain data on the characteristics and mechanical behavior of the lunar soil at the surface and subsurface and the variation of its properties in lateral and vertical directions, on slopes, and between different regions of the Moon. The equipment used included an adjustable sampling scoop, a self-recording penetrometer, core tubes, and the Apollo lunar surface drill and bore stems. Further soil testing could be done at LRL in Houston on returned soil samples, including the core tube and other geologic samples, especially the fine-grained soil sample. Photography requirements of this experiment were met with a battery-operated 16-mm data acquisition camera (DAC) with a 10-mm focal length lens, a Hasselblad electric data camera (HEDC) with a 60-mm focal length lens, and real-time TV transmissions. The astronauts performed the required trenching activity, penetrometer load plate and cone tests, and soil behavior/characteristic observations such as the LRV wheel/lunar soil interaction and LM footpad/soil interaction. After tests were completed, an astronaut removed the head from the penetrometer and stowed it for return to earth. This head contained the recording drum that indicated the penetrometer test results.

The Lunar Self-Recording Penetrometer (LSRP) had a mass of 2.3 kg and consisted of an upper cannister housing attached to the top of a long shaft and a reference pad assembly attached to the bottom. A recording drum was contained in the upper cannister and captured a record of each penetration. The LSRP was equipped with a 2.54 x 12.7 cm bearing plate and three penetrating cones with base areas of 1.29, 3.22, and 6.45 square cm and a 30 degree apex angle that could be attached to the bottom of the penetration shaft at the reference pad. The reference pad, which folded for storage, acted as a datum on the lunar surface for measurement of penetration depth. When an astronaut pushed on the upper end, the bearing plate or lower cone and shaft would penetrate into the lunar soil while the reference pad stayed on the surface. A retractor cable mechanism running from the reference pad to the upper housing actuated a stylus which would move axially along the recording drum to measure the depth of penetration. The force applied through the extension handle by the astronaut would deflect a calibrated coil spring which would cause the recording drum to rotate under the stylus by an amount prportional to the force. The maximum force caused a 30 degree rotation. The LSRP had a maximum penetration depth of 76 cm and the ability to measure penetration force to a maximum of 215 N.

The core tubes were thin-walled hollow aluminum tubes, 37.5 cm long with an inside diameter of 4.13 cm and an outside diameter of 4.38 cm. The lower tubes could be used individually or screwed together with an upper tube to make a longer, or double tube. The lower tube had a stainles steel bit on the bottom for penetrating the soil. A "keeper", a flat disk with the same inside diameter as the tube, fit inside the top end of the tube and an adapter was screwed on top. The tubes would be driven into the ground with a hammer as far as they could go. Then the keeper would be pushed down inside the tube by a long rod which fit into a hole in the top of the adapter. The keeper would be pushed to the top of the sample in order to keep the sample in place. The tube was then removed from the ground, the end coverd with a teflon cap, and the sample was brought back to Earth for analysis.

The Apollo lunar surface drill consisted of an electric drill with a set of long hollow bore stems which could be screwed together. The top of the drill had a battery pack and handle, directly underneath this was a power head and thermal shield. The drill stem extended from this through a treadle placed on the surface and into the regolith. At the bottom of the first drill stem was a 6 cm long drill bit with five tungsten-carbide blades. The drill was used to retrieve deep samples (down to 4.6 meters) of lunar regolith.

Eleven tests were made using the SRP during the second Apollo 16 EVA: four cone penetration tests at station 4 and five cone penetration and two plate load tests in the station 10 ALSEP area. Double core tube samples were taken from stations 4, 8, 10, and 10' and a single core tube sample from station 9, a total of over 6 kg of drive tube samples. A deep drill core was taken to a depth of 2.24 m in the ALSEP area.

Alternate Names

  • Apollo16ALSEP/SoilMechanics
  • Lunar Self-Recording Penetrometer
  • S-200
  • S200

Funding Agency

  • NASA-Office of Applications (United States)

Discipline

  • Planetary Science: Geology and Geophysics

Additional Information

Questions and comments about this experiment can be directed to: Dr. David R. Williams

 

Personnel

NameRoleOriginal AffiliationE-mail
Mr. M. MillerGeneral ContactNASA Johnson Space Center
Prof. James K. MitchellPrincipal InvestigatorUniversity of California, Berkeley

Selected References

  • Mitchell, J. K., et al., Soil Mechanics, in Apollo 16, Prelim. Sci. Rept., NASA SP-315, 8-1, Wash., DC, 1972.
  • Costes, N. C., et al., Cone penetration resistance test --- an approach to evaluating in-place strength and packing characteristics of lunar soils, Proc. Second Lunar Sci. Conf., 3, 1973-1987, M.I.T. Press, 1971.

Related Information at NSSDCA

Model of LSRP

Model of the Lunar Surface Recording Penetrometer (LSRP) at the National Air and Space Museum

Apollo 15 Soil Mechanics Experiment

Scanned Penetometer Data Online (Lunar Data Project)

Lunar Data Project

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